Not applicable.
Not applicable.
1. Field of the Invention
The present invention relates to a ventilated cage system, and in particular, to a ventilation air supply system that provides air to the entire cage receptacle and allows the air to leave the cage receptacle in the same manner without the need for a filter cap or bonnet. The cage receptacle lid comprises a permanently mounted seal to prevent cross-contamination with the room air and cage air. The improved ventilation system creates an even flow of air along the side of the cage receptacle thus providing an even air flow across the bottom of cage, and therefore providing a better environment for an animal.
2. Brief Description of the Related Art
Ventilated cage systems are well known in the art. Cages within the ventilated system traditionally are connected to a High Efficiency Particulate Air (HEPA) filtered air system for the protection of both the research animals and the laboratory personnel. The ventilated cage reduces heat, ammonia, and carbon dioxide concentrations in comparison to a static or non-ventilated cage. However, cages in a ventilated system must have the capability to be removed from the rack for feeding, cleaning and access to the animals. In addition, the cage must have the capability to maintain some type of air flow into the cage when removed from the ventilation system.
Information relevant to attempts to address the problems of providing a well-ventilated cage system that maintains sterility both when connected to the ventilation and during static periods can be found in the following U.S. patents. These references mentioned in this background section are not admitted to be prior art with respect to the present invention.
Filter caps or bonnets used with ventilated cage systems are well known in the art. During static ventilation, filter caps or bonnets are means to provide an air supply to the animal and yet minimize cross-contamination between cages and the external environment. Examples of filter bonnet cages may be found in U.S. Pat. Nos. 4,593,650; 5,000,120; and 6,158,387. Cages with filter caps or bonnets suffer from one or more of the following disadvantages. If the filter cap or bonnet does not encompass a protective plate, the filter is exposed such that an animal might damage the filter, rendering it ineffective and resulting in contamination. In addition, the filter must be regularly changed or replaced.
U.S. Pat. No. 4,480,587 to Sedlacek, which is incorporated herein by reference, discloses a cage containing a filter cap that has a substantially rigid transparent housing that rests on and encompasses the cage. A portion of the filter cap overhangs a portion of the cage to prevent the filter cap from being dislodged from the cage. An air filter is detachably secured to the roof portion of the filter cap and is protected from damages by a perforated steel plate.
However, personnel changing the filter are required to use tools to remove the protective plate to release the filter. The use of the tools requires additional resources and time. In addition, during the changing of the filter, the animal within the cage could escape through the open top.
In order to create a clean air system during non-static conditions, the prior art has utilized HEPA filtered air delivered into the cage. HEPA filtered air systems aid in the removal of heat, humidity, and unwanted micro-environmental vapors while the cage is on the rack. U.S. Pat. No. 5,000,120 to Coiro, Sr. et al., which is incorporated herein by reference, discloses a rack and cage combination that includes a forced air ventilation system that is automatically coupled to the cage when it is placed for storage on the rack. Coiro et al., also discloses that the filtered HEPA is directed downwardly with moderate velocity by the air supply tube. As such there will be a positive pressure in the cage that will result in air being exhausted from the cage primarily via the openings. The forced air system includes means for directing air down onto the floor of the cage whereby vapors that normally settle at the bottom of the cage are circulated vertically toward the bonnet filter. Coiro et al., also discloses ventilation passages around the periphery of the open top under the skirt of the filter bonnet so that gases, vapors, and particulate matter to freely pass out of the cage.
U.S. Pat. No. 5,148,766 to Coiro, Sr. et al., which is incorporated herein by reference, discloses an animal rack and cage system in which forced HEPA filtered air is introduced into the bonnet of each cage and removed from the periphery of the bonnet. A positive air probe is connected to a HEPA filter supply inlet manifold and is introduced into each cage through an aperture in the bonnet. Each ventilating probe includes a port that faces downwardly towards the bottom section of each cage. The air probe includes a port that faces downward towards the bottom of the cage. An L-shaped spacer separates the bonnet from the bottom section so that air exhaust ports in the U-shaped guide can remove exhausted air from the periphery of the cage.
U.S. Pat. No. 5,954,013 to Gabriel et al., which is incorporated herein by reference, discloses a ventilation cage and rack system, which maximizes cage density. Gabriel et al., discloses that the rack includes at least one air exhaust plenum, and at least one canopy disposed within said rack. The canopy is capable of supporting a first cage within the rack above the canopy, and also positioning a second cage below the canopy so as to maintain a gap between the top of the second cage and the canopy to permit air to be drawn into the air exhaust plenum from the interior of the second cage through the top of the second cage and to also permit ambient air to be drawn across the top of the second cage into the air exhaust plenum.
Each of these references suffers from the disadvantage of requiring a filter cap or bonnet as a means to minimize contaminates from passing into or out of the cage. Because filter caps or bonnets inhibit air movement, larger fans or blowers are required to move the HEPA filtered air throughout the ventilation system. Increased blower or fan sizes often produce excess noise either by mechanical or high frequency fluid noise. This excess noise in a holding facility can be harmful to the animals. Also, at least two fans, one for delivery and one for exhaust, are required to move the air throughout the ventilation system.
Likewise, allowing contaminates to freely pass out of the cage into the animal holding facility may also create a harmful environment for the animals. In addition, several references force the air directly into the cage at or near the water valve, which may be disruptive to the animal as it drinks. The limitations of the prior art are overcome by the present invention as described below.
The present invention is directed to an apparatus that satisfies the needs identified above. The invention comprises a ventilated cage receptacle encompassing a ventilation distribution chamber that can function during static or active ventilation. By altering the way the air is directed into the cage, a more even flow of air along the length of the cage is achieved. This present invention also minimizes the number of fans required. The invention utilizes a single fan to create a positive or negative pressure for air movement during active ventilation.
The cage receptacle comprises an integral ventilation distribution chamber that during forced or non-static ventilation distributes air to the entire cage receptacle and allows the air to leave the receptacle in the same manner. The ventilation air is distributed to one side of the cage receptacle wherein the air passes into a distribution chamber. The distribution chamber functions to maintain an even flow of air along the length of the cage and subsequently down to the floor of the cage. One embodiment of the invention is to change the area of the distribution chamber by a gradual taper along its length. The tapering of the distribution chamber creates a flow of supply air along the long side of the cage receptacle. The air passes into the distribution chamber containing small perforations. Gradually tapering the distribution chamber and maintaining a constant perforation size diverts the flow of air down the interior side wall of the cage receptacle. The air subsequently travels along the floor of the receptacle toward the opposite interior side wall of the cage. The air exits the cage receptacle by an integral distribution chamber on the opposite side of the cage. Because the exit distribution chamber has less internal pressure than the supply distribution chamber, the air freely moves into the exit distribution chamber. Air travels along the exit distribution chamber, into the integral biological barrier and subsequently out of the cage.
Another embodiment of the distribution chamber is to maintain a uniform cross sectional area of the distribution chamber along the length of the cage, but alter the size and/or frequency of the perforations along the length of the cage. By increasing the size of the perforations in the distribution chamber along its length, a more even flow of positive pressure air is achieved.
The invention also comprises an integral biological barrier that functions during static ventilation to significantly reduce contaminants entering the cage receptacle without the need for a filter cap or bonnet. The integral biological barrier is a chamber located inside the cage receptacle wherein the slow moving air must ascend vertically before entering the main housing area. During static ventilation the velocity of the air is not sufficient to lift the contaminants up the vertical ascent. Contaminants fall out of suspension as the air continues into the distribution chamber and subsequently the main housing area of the receptacle.
The distribution cover acts as the top cover of the distribution chamber. The distribution cover works both by diverting air down the cage receptacle. The invention further employs a unique process of permanently embedding a seal into the cage lid, thus creating a one-piece lid and seal. The seal embedded lid prevents cross contamination of room air and cage air. When the cage receptacle is placed into the ventilation rack system, a pressure means exert downward on the lid compressing the seal, thus preventing air from moving in or out around the rim of the cage lid. A benefit of the one-piece cage lid and seal is that the user will not have to clean and reinstall the seal every time the cage receptacle is cleaned or maintenanced.
It is therefore an object of the present invention to provide for a ventilation cage system that evenly distributes supply air along the length of the entire cage receptacle and allows the air to leave the receptacle in the same manner using a ventilation distribution chamber.
It is a further object of the present invention to provide for an integral biological barrier for static ventilation without the need for a filter cap or bonnet.
It is also an object of the present invention to provide an integrated cage seal to alleviate the need for the user to maintain and clean both the seal and cage lid.
It is still further an object of the present invention to provide an integrated seal within the cage lid to prevent cross contamination of room air and cage air.
These and other features, objects and advantages of the present invention will become better understood from a consideration of the following detailed description of the preferred embodiments and appended claims in conjunction with the drawings as described following: